CAN THO – Damming on the Mekong River mainstream, coupled with sand overexploitation, would not only hit aquaculture but also threaten the Mekong Delta’s existence in the future, experts told the Daily.

The Lao government last week started work on Don Sahong dam in Champasak Province, the second hydropower project on the river’s mainstream after Xayaburi, despite strong opposition from the downstream countries, including Vietnam.

The Lao government said the Don Sahong dam construction project will leave positive impact on socio-economic development and help alleviate poverty in the nation. In contrast, a number of Vietnamese experts have expressed concerns over a future decline in fish resources and over the future disappearance of the Mekong Delta.

Dr. Le Anh Tuan, deputy head of the Institute of Climate Change Research at Can Tho University, told the Daily that Laos did not go through the consultation process and ignored a request to stop construction of Don Sahong dam from Vietnam and Cambodia, both of them most vulnerable to the damming.

He added that Laos already began construction so Vietnam would find it difficult to persuade the neighboring country to suspend the project.

Tuan said Don Sahong and other hydropower dams on the Mekong River mainstream would heavily affect the downstream areas, especially in terms of fish and people’s livelihoods.

Xayaburi and Don Sahong dams are about two kilometers from the Lao boundary with Cambodia so it would cause fish stocks to fall in Cambodia first and then Vietnam, and will obstruct fish from migration.

Tuan said the Don Sahong dam would have insignificant impact on farming as it would be located in a tributary of the river. He said damming on the Mekong River mainstream and sand overexploitation in the Mekong Delta over the past time could cause the delta to disappear in the near future.

Tuan said the Mekong Delta took shape around 4,000-6,000 years ago when silt flowed from the upstream to the downstream but there would be no more silt when dams are built along the Mekong River.

A National University of Singapore study showed that silt from the upper reaches of the Mekong River to the Mekong Delta region in Vietnam fell to 75 million tons a year compared to 160 million tons following the completion of Manwan hydropower dam in China.

Tuan said it took thousands of years for the delta to take shape but just a few hundreds of years are enough to destroy this region.

Speaking to the Daily, Nguyen Huu Thien, an independent expert in ecology, shared Tuan’s view, saying that damming on the Mekong River mainstream leads alluvium to drop and sea waves to erode sedimentation, thus causing the delta to disappear within the next 100 years.

Tuan said the riverbed is much deeper at the moment as a result of damming. He put the blame on sand overexploitation in the Mekong Delta, coupled with Chinese damming in Yunnan Province.

He said water would flow faster, erode river banks and cause landsides. He proposed taking back licenses from sand exploiters and protecting land by building embankments and planting trees.

However, those short-term measures can only slow down the Mekong Delta’s disappearance. In the long run, Vietnam must negotiate with upstream countries to prevent construction of more dams in the Mekong River.